Carburetor



March 6, 1934. A. M. PRENTISS I I 1,950,266

CARBURETOR Filed Jan. 25, 1952 IN VEN TOR;

Augusvin M. Prenfiss Q %M v ATTORNEY.

Patented Mar. 6, 1934- 1.950.206 oAnBURE'ron Augustin M. Prentiss, San Antonio, Tex asslgnor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application January 25, 1932, Serial No. 588,757 12 Claims. (01. 261-34) This invention pertains to carburetors and more particularly has reference to pressure feed carburetors of the compensating type.

This invention is an improvement upon the inventions disclosed in my United States Patent No. 1,329,309, issued January 27, 1920, and in my copending application, Serial No. 590,296,'fi1ed 7 February 1, 1932, of which latter this application is a continuance in part.

In the copending application referred to I disclosed a pressure feed compensating carburetor wherein the liquid fuel and main air supplies were fed into the mixing chamber under atmos- I pheric pressure while the supplementary air supply, used to atomize the liquid fuel, was fed into the mixing chamber through'an atomizing nozzle and under such a variable pressure as would insure complete compensation of the fuel-air mixture under all operation conditions. While this arrangement, in general, gave very satisfactory results, some difliculty was experienced in securing a close control of the liquid fuel feed, especially at low speeds when the vacuum in the mixing .chamber was at or near a minimum. Under these conditions, the. feed of liquid fuel depends almost entirely upon the aspirating effect.

of the supplementary air discharged under superatmospheric pressure through the atomizingnozzle and variations in vacuum in the mixing chamber had only a slight secondary effect on the liquid fuel jet, being only that resulting from the corresponding increase or decrease in the discharge velocity of the compressed air from the.

nozzle.

I have found that this difiiculty can be completely obviated by slightly varying the head on the liquid fuel so as to raise the top of the liquid fuel column in the atomizing nozzle and bring it directly into the path of the escaping compressed air. When this is done the liquid fuel is then discharged by the direct expulsi ve force of the compressed air escaping from the nozzle and does not depend entirely upon aspiration to maintain its flow. Since this elevation of the level of the liquid fuel column in the atomizing nozzle is only necessary while the carburetor is in operation and should in general vary with the degree of throttle opening, I have found that the most efficient way in which to secure these results is to provide means whereby theJevel of the liquid fuel column in the nozzle is controlled by the throttle so that it rises as the throttle is opened and falls when the throttle is closed. In this way the normal static level of the liquid fuel in the nozzle (when the carburetor is not in operation) is below that of the end or the air tube in the nozzle and no leakage of liquid fuel from the carburetor can occur. Anobject of this invention is to devise a pressure feed compensating carburetor in which the 1 liquid fuel is fed into the mixing chamber by the expulsive force of compressed air issuing from an atomizing nozzle.

Another object of this invention is to provide a carburetor in which the liquid fuel is fed into the mixing chamber under a variable head which varies with the opening of the throttle.

Still another object ofthis invention is to provide a carburetor in which the head ofliquid fuel is above the end of the fuel nozzle while the carburetor is operating and which is below the end of the fuel nozzle when the carburetor is, not in operation. a Y With these and other objects in view which may be incident .to my improvements, my invention consists in'the combination and arrangement of elements hereinafter described and illustrated in the accompanying drawing which shows in central longitudinal section a carburetor embodying my invention.

This invention broadly comprehends a carburetor having the general features and operating principles described in my copending application, above identified, and in addition thereto, means for lowering the top of the fuel nozzle 35 as the throttle is opened and means for raising the level of the liquid fuel in the carburetor float reservoir alsoas the throttle; these two means being independent of each other so that either or both of them may be employed in a carburetor of the type described. 1

Referring to the drawing, the reference numeral 1 denotes the body of a carburetor having. a main air inlet 2, Venturi throat 3, mixing chamher 4 and mixture outlet 5 controlled by a butterfly throttle valve 6 in the usual manner. Integral with the bottom wall of air inlet 2 and extending to a point just above the center of the Venturi throat 3, is an atomizing nozzle 7 consisting of an outer liquid fuel tube 8, and an inner air tube 9. Slidably mounted in tubes 8 and 9 are a pair of concentric tubes 10 and 11 held in spaced relation to each other by a spider 12 and adapted to telescope into and variably prolong tubes 8 and 9 respectively, as clearly shown in the drawing. Surmounting tube 10 and adjustably attached by screw threads is a cap 13 having a central aperture.14 through which liquid fuel and air from tubes 8 and 9 are discharged into the mixing chamber 4.

Near its upper end tube has a pair of cars to which are pivotally connected an adjustable link 16 which in turn is pivotally connected to a pair of cars 17 on throttle 6, so that tubes 10 and 11 are raised and lowered as the throttle 5 is closed and opened.

Tube 8 communicates through a passageway 18 and port 19 with liquid fuel reservoir 20 which is supplied with liquid fuel under superatmospheric pressure through pipe 21 and inlet 22 from a pump geared to the engine (not shown). Inlet 22 is controlled by a valve 23 which is actuated by a float 24 so that the liquid level in the reservoir is constantly maintained at a fixedlevel X'X in the usual manner. The buoyant force of the float 24 is sufficient to close valve 23 against the pressure of the liquid fuel in pipe 21 at all times. Port 19 is controlled by a manually adjustable needle valve 25 which regulates the flow of liquid fuel from reservoir 20 to nozzle land determines the quality of the fuel-air mixture.

Tube 9 communicates through an air passageway 40 and pipe 41 which has a compressed air pump geared to the engine (not shown). While the carburetor is in operation compressed air is constantly supplied to nozzle 7 in such quantities which has an atmospheric vent 42 and seats on gasket 27 and is held in place by a series of screws 28. Extending upwardly from the top of cover 26 is a boss 29 which functions as a guide sleeve for a stem 30 which is attached by screw-threads to a float 31 arranged to float in the: liquid fuel in reservoir 20 without interfering with float 24. The upper end of stem 30 is bifurcated and the two arms thus formed embrace a roller 32 which is held by a spring 33 in contact with a lever 34 pivoted at 35 on the body 1 of the carburetor. y

A washer'36 threaded over stem 30 bears against the arms at the-top of stem 30 and transmits the force of spring 33 to the stern.

Throttle 6 is fixed to a shaft 37 which is journalled in the walls of mixture outlet 5 and carries fixedly attached a cam 38 and an operating lever 39. which is attached to the acceleration pedal of the car (not shown) in the usual way. Cam 38 is so arranged as to depress lever 34 as a the throttle 6 is opened in opposition to spring 33 and the buoyant force of float 31 which serve to.

raise lever 34 whenever throttle 6 is closed. Whenever lever 34 is depressed by the opening of throttle 6 it in turn submerges float 31 further into the liquid fuel in reservoir '20 and thus raises the liquid level therein above the normal static level XX. This rise in the liquid fuel level in reservoir 20 operates to increase the head of liquid fuel in tubes 9 and 10 and bring the liquid level above the end of said tubes directly into the path of the compressed air issuing from tube 11. g This is also the effect produced whenever tubes 10 and 11 are lowered by the opening of the throttle, so that the two effects supplement each other and are additive. From what has just been said it is clear thateither the lowering of the nozzle or the raising of the liquid level in reservoir 20 may be made alone sufficient to give the in creased liquid head on the fuel in the nozzle 7 and hence either device may be employed alone, or in combination as shown in the drawing.

By raising the liquid level in nozzle 7 so that the liquid level is above the top of tube 11, the liquid fuel is subjected to the expulsive force of the compressed air escaping from the tube 11 and is thus forcibly ejected through aperture 14 and issues in the form of a highly atomized spray.

Since the throttle is always closed by spring 33 when the carburetor is not in operation, the end of tube 10 is automatically raised above the liquid level XX in reservoir 20 and hence no leakage of liquid fuel from the carburetor can occur when the carburetor is not in operation.

While I have shown and described the preferred embodiment of my invention I desire it to be understood that I do not limit myself to the precise details of, construction shown by way of illustration as these may be readily changed and modified by-those skilled in the art without departing from the spirit of my invention or exceeding the scope of the appended claims.

I claim:

1. In a carburetor having a throttle, an atomizing nozzle comprising an air tube and a liquid fuel tube, a liquid fuel reservoir communicating with said nozzle, and means for varying the height 7 of said nozzle and the liquid level in said reservoir in proportion to the movement of the throttle 2. In a carburetor having a throttle, an atomizing nozzle comprising an air tube and'a liquid fuel tube, a liquid fuel reservoir communicating with said nozzle, and means for decreasing the height of said nozzle and increasing the depth of liquid fuelin said reservoir as the throttle is opened.

3. In a carburetor, a throttle, a liquid fuel reservoir, an atomizing nozzle having a compressed air tube and a liquid fuel tube, and means actuated by said throttle for raising the discharge ends .of-said tubes. above the static level of liquid fuel in said reservoir when said carburetor is not in operation and for lowering the end of said nozzle below said level when said carburetor is in operation.

4. In a carburetor, an atomizing nozzle comprising an air tube and a liquid fuel tube, and means to raise the level of the liquid'fuel in said fuel tube above the end of said air tube whenever the carburetor is in operation whereby said air tube is completely submerged in liquid fuel and the liquid fuel is thereby discharged from said nozzle by the expulsive force of the air issuing from said air tube.

by discharged from said nozzle by the expulsive forceof the air issuing from said air'tube.

.6. In a carburetor having a throttle,'an atomizing nozzle comprising a compressed air tube and a liquid fuel tube, and means for simultaneously varying the levels of the discharge ends of said tubes with the movement of the throttle, whereby the liquid fuel is brought directly across the path of the air jet in said'nozzle and is thereby positively expelled from said nozzle.

7. In a carburetor having a throttle, an atomizing nozzle comprising a compressed air tube and a the air jet in said nozzle and is thereby positively expelled from said nozzle.

8. In a carburetor having a throttle, an atomizing nozzle comprising a compressed air tube and a liquid fuel tube, and means for simultaneously fit varying the heights of said tubes with the move ment of the throttle, whereby the liquid fuel is brought directly across the path of the air jet in said nozzle and is thereby positively expelled from said nozzle.

9. In a carburetor having a throttle, a liquid fuel reservoir, an atomizing nozzle communicating with said reservoir and comprising a compressed air tube and a liquid fuel tube, and means for lowering the level of the discharge end of said air tube below the fuel level in said reservoir as said throttle is opened, whereby the liquid fuel is brought directly across the path of the air jet in said nozzle and thereby positively expelled from said nozzle.

10. In a carburetor having a throttle, a liquid fuel reservoir, an atomizing nozzle communicating with said reservoir and comprising a compressed air tube and a liquid fuel tube, and means for lowering the level of the discharge end of said air tube below the fuel level in said reservoir in proportion to the opening of the throttle, whereby the liquid fuel is brought directly across the path of the air jet in said nozzle and is thereby positively expelled from said nozzle;

11. In a carburetor having a throttle, a liquid fuel reservoir, an atomizing nozzle communicating with said reservoir and comprising a compressed air tube and a liquid fuel tube, and means for lowering the discharge ends of said tubes simultaneously below the fuel level in said reservoir as the throttle is opened, whereby the liquid fuel is brought directly across the path of the air jet in said nozzle and is thereby positively expelled from said nozzle.

12. In a carburetor having a throttle, a liquid fuel reservoir, an atomizing nozzle communicating with said reservoir and comprising a compressed air tube and a liquid fuel tube, and means for simultaneously lowering the levels of the discharge ends of said tubes below the liquid fuel level in said reservoir in proportion to the opening of the throttle, whereby the liquid fuel is brought directly across the path of the air jet in said nozzle and is thereby positively expelled from said nozzle.

AUGUSTIN M. PRENTISS. 

